title: Multi-level modelling of physical activity in nuclear families.
abstract: BACKGROUND
  Few studies focus on the different dyadic relations among family members to study physical activity (PA) levels.
  
  
  OBJECTIVE
  The aim was to investigate predictors and sources of variance of PA levels in nuclear families using multi-level modelling.
  
  
  METHODS
  The sample consisted of 2661 Portuguese four-member nuclear families (10 644 subjects). PA was measured using a questionnaire and socioeconomic status (SES) was assessed by parental occupation. Height and weight were measured in children, while parents self-reported their values.
  
  
  RESULTS
  The results showed that intra-generational similarities were higher than inter-generational, with correlation values of 0.26 and 0.10, respectively. SES was unrelated to any family members' PA level. Being male (β = 0.26, t = 21.77), being older (β = -0.36, t = -4.73) and greater BMI for mothers (β = 0.02, t = 2.55) had effects on individuals' PA.
  
  
  CONCLUSIONS
  These results suggest a strong dyadic resemblance in PA, showed different effects of gender, age and BMI on individuals' PA and demonstrated that multi-level modelling is a useful strategy to study PA in families.
authors.affiliation: CIFI2D, Kinanthropometry Lab, Faculty of Sport, University of Porto , Porto , Portugal .
authors.forename: Thayse Natacha Queiroz Ferreira
authors.initials: TN
authors.lastname: Gomes
authors.forename: Fernanda Karina
authors.initials: FK
authors.lastname: Dos Santos
authors.forename: Rui Manuel
authors.initials: RM
authors.lastname: Garganta
authors.forename: David A
authors.initials: DA
authors.lastname: Kenny
authors.forename: Peter T
authors.initials: PT
authors.lastname: Katzmarzyk
authors.forename: José António Ribeiro
authors.initials: JA
authors.lastname: Maia
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D009043:Motor Activity / Q000502:physiology*; D009679:Nuclear Family; D009765:Obesity; D010287:Parent-Child Relations; D010290:Parents; D011174:Portugal; D012737:Sex Factors; D012923:Social Class; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires